IMPROVED PROCESS OF ULTRASONIC SPRAY PYROLYSIS DEPOSITION OF ONE OR MORE ELECTROCHROMIC AND/OR ELECTROLYTIC FILMS ON A SUBSTRATE

Abstract

A process of making an electrochromic or an electrolytic film by Ultrasonic Spray Pyrolysis (USP) deposition on a substrate comprising: mixing a surfactant to an aqueous precursor solution comprising an electrochromic component or an electrolytic component to provide a spray solution; introducing the spray solution into an ultrasonic spray deposition nozzle at a constant flow rate between 0.1 mL/min and 2 mL/min and applying an ultrasonic frequency between 80 and 120 kHz to generate atomized droplets of the precursor solution; entraining the atomized droplets with a controlled jet of air as gas carrier at a pressure between 0.50 to 2.0 psi, onto a pre-heated substrate at a temperature of 200 to 450° C.; thermally converting the atomized droplets when depositing onto the pre-heated substrate to generate an electrochromic or an electrolytic film.

Claims

1. A Process of making an electrochromic or an electrolytic film by Ultrasonic Spray Pyrolysis (USP) mixing a surfactant with an aqueous precursor solution comprising an electrochromic component or an electrolytic component to provide a spray solution; introducing the spray solution into an ultrasonic spray deposition nozzle at a constant flow rate between 0.1 mL/min and 2 mL/min and applying an ultrasonic frequency between 80 and 120 kHz to generate atomized droplets of the precursor solution; entraining the atomized droplets in a controlled jet of air as gas carrier at a pressure between 0.50 to 2.0 psi, onto a pre-heated substrate at a temperature of 200 to 450° C.; thermally converting the atomized droplets when depositing onto the pre-heated substrate to generate an electrochromic or an electrolytic film.

2. The process according to claim 1 wherein the constant flow rate is between 0.1 and 0.4 mL/min with a spray nozzle.

3. The process according to claim 1 wherein the film deposition onto the preheated substrate is designed according to a three-dimensional pattern by the ultrasonic spray deposition nozzle.

4. The process according to claim 1 wherein the three-dimensional pattern follows a S shape are move in the X-Y plane.

5. The process according to claim 1 wherein both steps of entraining the atomized droplets and their thermal conversion onto the pre-heated substrate are repeated between 2 to 16 times, in order to generate an homogenous electrochromic or electrolytic layer.

6. The process according to claim 1 wherein the electrochromic film comprises a metal oxide selected from tungsten oxide, molybdenum oxide, niobium oxide, titanium oxide, copper oxide, chromium oxide, manganese oxide, vanadium oxide, tantalum oxide, iron oxide, cobalt oxide, nickel oxide, ruthenium oxide, rhodium oxide, palladium oxide, osmium oxide, iridium oxide, platinum oxide or a combination thereof.

7. The process according to claim 6 wherein the electrochromic film further comprises a dopant element selected from hydrogen ion, deuterium ion, lithium ion, sodium ion, potassium ion, rubidium ion, caesium ion, molybdenum ion, titanium ion, vanadium ion, calcium ion, barium ion, magnesium ion, strontium ion, tungsten ion, nickel ion and combination thereof.

8. The process of making an electrochromic film according claim 1 wherein the aqueous precursor solution comprises an organic or inorganic salt or complex, selected from nitrate, chloride, acetate, acetylacetonate, citrate, sulphate, peroxometalate, containing metal selected from tungsten, molybdenum, niobium, titanium, copper, chromium, manganese, vanadium, tantalum, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum or a combination thereof.

9. The process according to claim 1 wherein the electrochromic layer is lithium doped nickel oxide or tungsten trioxide

10. The process of making an electrolytic film according to claim 1 wherein the aqueous precursor composition comprises an electrolytic component selected from tetraethyl orthosilicate, lithium nitrate, aluminium nitrate, zinc nitrate, nitric acid, boric acid, phosphoric acid, lithium sulfate, or a combination thereof.

11. The process according to claim 1 wherein the electrolytic film is selected from lithium aluminosilicate (LAS), lithium borosilicate (LBS) or lithium phosphosilicate (LPS).

12. The process according to claim 1 wherein the surfactant is polyethylene glycol.

13. The process according to claim 1 wherein the weight ratio of the electrochromic component to polyethylene glycol in the aqueous precursor solution is between 10:1 and 1:10.

14. The process according to claim 1 wherein the ultrasonic frequency is 120 kHz.

15. The process according to claim 1 wherein the carrier air gas pressure is 0.90 psi.

16. The process according to claim 1 wherein the substrate is pre-heated at a temperature of 350° C.

17. The process according to claim 1 wherein the substrate is fluorine doped tin oxide coated glass.

18. A multilayer stacking construction on a substrate comprising at least one electrochromic layer and at least one electrolytic layer generated by the process according to claim 1.

19. The multilayer stacking construction on a substrate according to claim 18 further comprising an additional electrochromic layer acting as a counter electrode.

20. The multilayer stacking construction according to claim 18 comprising: a fluorine doped tin oxide coated glass substrate; a first layer generated on the substrate and selected from lithium doped nickel oxide or tungsten oxide; a second layer of lithium aluminosilicate generated on the first layer; a third layer generated on the second layer and selected from tungsten oxide or lithium doped nickel oxide; as counter electrode and a fourth conductive top layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] FIG. 1 illustrates the arc pattern according to which the ultrasonic spray nozzle is moved above the substrate surface during the ultrasonic spray deposition process.

[0061] Typical spacing value between two arcs is 4 mm. The deposition pattern may be repeated 2-16 times, keeping exactly the same pattern every odd passages and shifting “x” or “y” coordinates by half of the spacing value (here 2 mm) every even passages.

[0062] FIG. 2 illustrates the AccuMist spray nozzle and its schematic representation (manufactured by Sono-Tek). This nozzle is used in the process according to the present invention.

[0063] FIG. 3 illustrates the impact Edge spray nozzle and its schematic representation (manufactured by Sono-Tek)). This nozzle can also be used in the process according to the present invention, especially on large scale substrates.

[0064] FIG. 4 illustrates cyclic voltammograms (dash lines)/transmittance (solid lines) curves obtained for electrochromic films deposited by the process according to the invention. An evolution of transmittance (λ=550 nm) and current density vs. potential (10 cycles, 20 mV/s) is reported from −1.74 to +1.06 V/Ag—AgNO.sub.3, in 0.5 M LiClO.sub.4/propylene carbonate for Li—NiO (up) and WO.sub.3 (down) electrochromic films deposited through USP at 350° C. on Glass/FTO substrates.

[0065] FIG. 5 illustrates evolution of reversibility during cyclic voltammetry (20 mV/s, from −1.74 to +1.06 V/Ag-AgNO.sub.3, 100 cycles, 0.5 M LiClO.sub.4/propylene carbonate solution) of Li—NiO (curve with dots) and WO.sub.3 (curve with triangles) electrochromic films deposited through USP at 350° C. on Glass/FTO substrates.

[0066] FIG. 6 illustrates evolution of transmittance (λ=550 nm) related to double-step chronoamperometry (current density vs. time) curves measured in 0.5 M LiClO.sub.4/propylene carbonate solution of Li—NiO (up) and WO.sub.3 (down) electrochromic films deposited through USP at 350° C. on Glass/FTO substrates. Potential values of +1.06 and −1.74 V/Ag—AgNO.sub.3 are consecutively applied for 3 min (each step) for promoting the coloration and bleaching (respectively) of Li—NiO films, while potential values of −1.74 and +1.06 V/Ag—AgNO.sub.3 are consecutively applied for 3 min (each step) for promoting the coloration and bleaching (respectively) of WO.sub.3 films. 4 cycles of measurements are recorded in each case.

[0067] FIG. 7 illustrates scanning electron microscopy images of Li—NiO (left), LAS (center) and WO.sub.3 (right) films deposited through USP at 350° C. on Glass/FTO substrates. All layers testify for high homogeneity, uniformity and smoothness.

[0068] FIG. 8 consists of FIG. 8A and FIG. 8B and illustrates the evolution of transmittance at 550 nm related to double-step chronoamperometry curves recorded 1 day (Figure SA) and 1 year (Figure SB) after the whole sample preparation. Potential values of −2.0 and +2.0 V are consecutively applied for 5 (1 day; Figure SA) or 3 min (1 year; FIG. 8B) (each step) for promoting the coloration and bleaching (respectively) of the device. 6 cycles of measurements are recorded in each case.

DETAILED DESCRIPTION OF THE INVENTION

[0069] The process according to the invention is now illustrated in the following examples using Glass/TCO as substrate, wherein TCO is fluorine-doped tin oxide (FTO).

[0070] Different mono- or/and multilayered systems were obtained according to the following scheme: [0071] An Ultrasonic Spray Pyrolysis (USP) deposition of individual electrochromic stoichiometric or non-stoichiometric lithiated nickel oxide layer Li.sub.y—NiO.sub.x (further denoted as “Li—NiO”), electrochromic stoichiometric or non-stoichiometric tungsten oxide layer WO.sub.(3-y) (further denoted as “WO.sub.3”) and electrolytic lithium aluminosilicate (further denoted as “LAS”) layer (see step I of Scheme 1); [0072] An USP deposition of electrochromic+electrolytic bilayers, following different combinations: Li—NiO/LAS or WO.sub.3/LAS (see step II of scheme 1); [0073] An USP deposition of electrochromic+electrolytic+electrochromic trilayers, following different deposition orders: Li—NiO/LAS/WO.sub.3 or WO.sub.3/LAS/Li—NiO (see step III of Scheme 1).

[0074] The process according to the invention may comprise the following steps: [0075] 1. Preparation of a spray solution from the precursor solution of electrochromic or electrolytic layer; one or more surfactants may be incorporated to this precursor solution; [0076] 2. Ultrasonic spraying of the spray solution onto the pre-heated Glass/TCO substrate according to a x,y-move arc pattern (which can be repeated several times) of the spray nozzle at a constant z distance above the whole substrate: the ultrasonically produced spray is entrained in a gas stream (air) onto the heated surface, where the deposited atomized droplets undergo a thermal conversion reaction resulting in the generation of a thin oxide film presenting electrochromic or electrolytic features; [0077] 3. In the case of a stacking procedure, targeting the elaboration of a full solid inorganic electrochromic device, steps 1 and 2 above are repeated with precursor solutions of electrochromic layer (WO.sub.3 or Li—NiO; step 1) and electrolytic layer (LAS; step 2) to generate a bilayered (electrochromic+electrolytic) or a trilayered (electrochromic+electrolytic+electrochromic) stacking onto the Glass/TCO substrate. However, a single electrochromic monolayer (Li—NiO or WO.sub.3) can also be used as a constituent in another stacking construction for electrochromic device (for instance, through lamination with another electrochromic layer and an electrolyte layer based on polymer gels or other materials—by lamination it is intended the permanent assembly of two separate materials by the action of pressure, heat or adhesive strengths; for such stacking construction the man skilled in the art will refer for instance to Zelazowska et al. in Journal of Non-Crystalline Solids 354 (2008) 4500-4505, Al-Kahlout et al. in Ionics 16 (2010) 13-19, . . . ). [0078] 4. A conductive top layer as described above is deposited on the multilayer stacking.

[0079] Experimental Protocols in Our Process According to the Invention

[0080] Experimental protocols involve 2.0×2.0×0.4 cm Glass/FTO substrates (Planibel GFast, 15 ohm/square). “Standard” parameters for USP deposition rely on the use of the Exactacoat USP device from Sono-Tek, with AccuMist ultrasonic nozzle, with apical spraying geometry, operated at 120 kHz. Solution flow rate is maintained constant at 0.25 mL/min, with clean air as carrier gas at 0.90 psi. The ultrasonically produced spray at the tip of the nozzle is then apically entrained in the low pressure air stream to finally reach the substrate, which temperature is set to 350° C. Deposition follows a “x,y” patterning above the surface according to an arc pattern with a S-shaped move (4 mm spacing) at a constant speed of 40 mm/s, with a constant z distance between nozzle and substrate of 5.5 cm. The substrates are maintained 5 min before and after the spraying on a heating plate to reach the desired temperature of 350° C. at the surface of the substrate before spraying and to promote the decomposition of the precursor after spraying. The “x,y” deposition is repeated several times keeping exactly the same pattern every odd passages and shifting “x” or “y” coordinates by 2 mm every even passages (see FIG. 1).

[0081] Parameters proper to each individual layer: [0082] Li—NiO electrochromic layer (I on Scheme 1): the precursor solution is made of 0.1 M NiNO.sub.3.6H.sub.2O+LiNO.sub.3 5% wt in purified H.sub.2O+polyethylene glycol (PEG) surfactant of Mw 400 (at a weight ratio m.sub.NiNO3:m.sub.PEG=1:3). USP deposition is performed by 10 consecutive passages of the AccuMist nozzle above the whole Glass/FTO surface. The resulting layers properties are described in the following Table 1 and illustrate a high reversibility, very fast coloration and bleaching times, a high coloration contrast, a very high coloration efficiency, and a quite low haze for such an electrochromic Li—NiO layer. [0083] LAS electrolytic layer (II on Scheme 1): the layer is synthezised from a sol-gel protocol in a EtOH/(purified)H.sub.2O solution with a 0.13 weight ratio, and is constituted of Al.sub.2O.sub.3 25% mol (from Al(NO.sub.3).sub.3.9H.sub.2O˜1.1 M), Li.sub.2O 25% mol (from LiNO.sub.3 ˜1.1 M), and SiO.sub.2 50% mol (from TEOS Si(OCH.sub.2CH.sub.3).sub.4˜1.1 M; H.sub.2O/TEOS=32.43). Precursor solution pH is fixed at 0.22 (adjusted with HNO.sub.3), before being diluted in H.sub.2O by a 50 factor. The PEG surfactant of Mw 400 is then added (6.0 g) to 20.0 mL of the diluted solution. USP deposition is performed by 6 to 8 consecutive passages. The resulting layers properties are described in the following Table 2 and illustrates a low haze with a high conductivity for such an electrochromic solid LAS layer. [0084] WO.sub.3 electrochromic layer (Ill on Scheme 1): the precursor solution is made of 0.01 M ammonium metatungstate AMT ((NH.sub.4).sub.6W.sub.12O.sub.39.4H.sub.2O) in purified H.sub.2O+PEG surfactant of Mw 400 (at a weight ratio m.sub.AMT:m.sub.PEG=1:10). USP deposition is performed by 6 consecutive passages. The resulting layers properties are described in the following Table 3 and illustrate a very high reversibility, moderately fast coloration and bleaching times, a very high coloration contrast, a high coloration efficiency, and a moderately low haze for such an electrochromic WO.sub.3 layer
Example with Different Nozzles:

[0085] Two different nozzle types were tested. AccuMist nozzle (Sono-Tek) (see FIG. 2) implies an apical spraying geometry, very useful in a 3D pattern as described above, while Impact Edge nozzle (Sono-Tek) (see FIG. 3) creates a fan-shaped spray pattern, which can be more suitable for larger size surfaces of (at least) 10×10×0.4 cm (Glass/FTO substrates).

Main Characteristics of Individual Layers Obtained Through Our Process According to the Invention

[0086]

TABLE-US-00001 TABLE 1 properties (optimal performances at room temperature) of Li—NiO layers obtained through the process according to the invention carried out with a spray nozzle. Li—NiO Thickness (nm) 260-270 Roughness (nm) 6 Crystal phase Cubic Li.sub.0.2Ni.sub.1.8O.sub.2 Reversibility-First CV cycle (%) 84 (*)   Coloration time-t.sub.c (s) 6 (**) Bleaching time-t.sub.b (s) 5 (**) Coloration contrast T.sub.b-T.sub.c (%) 54 (85-31) (**) (λ = 550 nm) Coloration efficiency = 41.2 log(T.sub.b/T.sub.c)/Q(cm.sup.2/C) L*/a*/b* parameters: 73.8/1.9/8.6- colored state-bleached state 95.5/−0.6/2.6 Haze (%) 1.0-1.3

TABLE-US-00002 TABLE 2 properties (optimal performances at room temperature) of LAS layers obtained through the process according to the invention carried out with a spray nozzle. LAS Thickness (nm) 360-370 Roughness (nm) 46 Crystal phase Amorphous Reversibility- No application First CV cycle (%) Coloration time-t.sub.c (s) No application Bleaching time-t.sub.b (s) No application Coloration contrast T.sub.b-T.sub.c (%) No application λ = 550 nm Coloration efficiency = No application log(T.sub.b/T.sub.c)/Q(cm.sup.2/C) L*/a*/b* parameters: No application colored state-bleached state Haze (%) 1.2-2.0 Conductivity (S/cm) 1.45 × 10.sup.−6

TABLE-US-00003 TABLE 3 properties (optimal performances at room temperature) of WO.sub.3 layers obtained through the process according to the invention carried out with a spray nozzle. WO.sub.3 Thickness (nm) 220-230 Roughness (nm) 2-4 Crystal phase Amorphous Reversibility- 94 (*)  First CV cycle (%) Coloration time-t.sub.c (s) 28 (**) Bleaching time-t.sub.b (s) 11 (**) Coloration contrast 83 (91-8) (**) T.sub.b-T.sub.c (%) λ = 550 nm Coloration efficiency = 26.1 log(T.sub.b/T.sub.c)/Q (cm.sup.2/C) L*/a*/b* parameters: 35.0/5.0/−29.9- colored state- 98.6/−0.2/0.5 bleached state Haze (%) 1.6-2.1
(*) Cyclic voltammograms/transmittance curves and evolution of reversibility upon cycling are presented on FIGS. 4 and 5, respectively.
(**) Double-step chronoamperometry/transmittance curves are presented on FIG. 6.

[0087] Example of reversibility and stability of the electrochromic films obtained by the process according to the invention.

[0088] A cyclic voltammetry and transmittance measurement was performed in 0.5 M LiClO.sub.4/propylene carbonate solution on an electrochromic film of Li—NiO and WO.sub.3 deposited through USP at 350° C. on a glass/FTO substrate.

[0089] FIG. 4 illustrates transmittance at λ=550 nm and current density vs. potential (10 cycles, 20 mV/s) reported from −1.74 to +1.06 V/Ag—AgNO.sub.3, and illustrates a good reversibility of respectively 84 and 94% for Li—NiO and WO.sub.3 electrochromic films prepared according to the process of the invention.

[0090] FIG. 5 illustrates an evolution of reversibility during the cyclic voltammetry measurement at 20 mV/s from −1.74 to +1.06 V/Ag—AgNO.sub.3 during 100 cycles for Li—NiO and WO.sub.3 electrochromic films. Both films remain stable (reversibility values always closer to 100%) during the 100 cycles test.

[0091] Example of coloration/bleaching performances of the electrochromic films obtained by the process according to the invention

[0092] The general working principle of the electrochromic device is based on the reversible double electrochemical injection of positive ions (Li.sup.+) and electrons inside and outside the networks of WO.sub.3 (working electrode, WE) and Li—NiO (counter electrode, CE) layers. The coloration mechanism involves the reduction of W and Li.sup.+ insertion at the WE (cathodic coloration) simultaneously to the oxidation of Ni and Li.sup.+ extraction at the CE (anodic coloration). The bleaching mechanism is based on the opposite processes, and both mechanisms are fully reversible.

[0093] A chronoamperometry measurement was performed in 0.5 M LiClO.sub.4/propylene carbonate solution on an electrochromic film of Li—NiO and WO.sub.3 deposited through USP at 350° C. on a glass/FTO substrate. FIG. 6 illustrates the evolution of transmittance at 550 nm related to double-step chronoamperometry (current density vs. time) curves for which potential values of +1.06 and −1.74 V/Ag—AgNO.sub.3 are consecutively applied for 3 min (each step) for promoting the coloration and bleaching (respectively) of Li—NiO films, while potential values of −1.74 and +1.06 V/Ag—AgNO.sub.3 are consecutively applied for 3 min (each step) for promoting the coloration and bleaching (respectively) of WO.sub.3 films. 4 cycles of measurements are recorded in each case.

[0094] Coloration and bleaching kinetics testify for very fast coloration and bleaching times of respectively 6 and 5 s for Li—NiO, and 28 and 11 s for WO.sub.3. In addition, high optical contrast of 54 and 83% are respectively measured for Li—NiO and WO.sub.3.

[0095] Example of morphological properties of the electrochromic and electrolytic films obtained by the process according to the invention

[0096] Scanning electron microscopy measurements are performed on Li—NiO, LAS and WO3 films deposited through USP at 350° C. on a glass/FTO substrate. FIG. 7 illustrates the very high degree of smoothness, uniformity and homogeneity in each case and all over the surfaces, as well as relatively low haze values comprised between 1 and 2%.

[0097] Example of Multilayer Stacking Obtained by the Process According to the Invention

[0098] Consequently we can use a “tandem” combination of a WO.sub.3 working electrode and a Li—NiO counter electrode (or in reverse order) in different configurations. In the particular case of a stacking construction, Li.sup.+ insertion/extraction processes are achieved through the intermediate electrolyte layer, acting thus as a Li.sup.+ ion tank.

[0099] The USP deposition process (at atmospheric pressure) according to the invention can thus advantageously be used to prepare a multilayer stacking construction through the progressive stacking of the different layers, which can be proceeded for example following the deposition order Li—NiO/LAS/WO.sub.3 (as presented on Scheme 1) as well as WO.sub.3/LAS/Li—NiO.

[0100] An electrochromic evaluation of such “all solid” multilayer stacking construction may be achieved through a chronoamperometry measurement performed on a WO.sub.3/LAS/Li—NiO stacking (illustrative case), which was continuously deposited through USP at 350° C. on a glass/FTO substrate, and covered (cathodic arc deposition) by a thin Au layer for conductivity purposes. WO.sub.3 layer on glass/FTO substrate acts thus as working electrode, while Li—NiO layer connected to Au top coating acts as counter electrode. FIG. 8 illustrates the evolution of transmittance at 550 nm related to double-step chronoamperometry curves recorded 1 day (FIG. 8a) and 1 year (FIG. 8b) after the whole sample preparation. Potential values of −2.0 and +2.0 V are consecutively applied for 5 (1 day; FIG. 8a) or 3 min (1 year; FIG. 8b) (each step) for promoting the coloration and bleaching (respectively) of the device. 6 cycles of measurements are recorded in each case. A good global coloration contrast is obtained (up to 54%), while coloration/bleaching kinetics are kept within several dozens of seconds, with fastest values of 12 s for coloration and 32 s for bleaching. Such performances remain globally stable after 1 year of sample ageing in ambient atmosphere (FIG. 8a vs. 8b), which proves the durability of the device. The device also testifies for high voltammetric cycling stability and reversibility. At least 1500 cycling (optically monitored) have been achieved.

[0101] The present invention also allows for the preparation of multilayer stacking following other processes, for instance via the encapsulation of an electrolytic layer made of polymer gel between WO.sub.3 and Li—NiO electrochromic layers USP-deposited on Glass/FTO substrates.

[0102] The present invention also allows for the preparation of a device based on a single electrochromic Li—NiO or WO.sub.3 layer deposited by USP on a Glass/FTO substrate, and acting as working electrode. This can be further encapsulated with an electrolytic layer (e.g. polymer gel) on a Glass/FTO substrate acting as counter electrode.